末次盛冰期临沂城区段的沂河古河槽

The Yihe River's paleo-valley in Linyi urban reach in the Last Glacial Maximum

选择沂河临沂城区段作为研究河段，根据九曲沂河大桥附近、G327沂河大桥附近的地质勘探钻孔资料，绘制了九曲沂河大桥附近、G327沂河大桥附近沂河古河槽地质剖面示意图，并在临沂城区段沂河河槽底部及岸边进行了采样分析。研究发现，沂河古河槽底部断裂带发育，G327沂河大桥附近约56 m以下的河槽为末次盛冰期时的沂河河槽，九曲沂河大桥附近约53-55 m以下河槽为末次盛冰期时沂河、祊河的古河槽；末次盛冰期，祊河在九曲沂河大桥的下游汇入沂河，沂河古河槽宽深比较大，河槽宽浅，具有分汊–辫状河特征。

The Linyi urban reach of the Yihe River was selected as the research reach. Two stratigraphical cross-sections of paleo-valley were established with bore datum near Jiuqu Yihe River Bridge and G327 Yihe River Bridge. And we also analyzed the samples from bottom and bank of the Yihe River in Linyi urban reach. The results showed that： the Yihe River’s paleo-valley located on the fault zone. In the Last Glacial Maximum, the paleo-valley of Yihe River laid 56 m below near G327 Yi River Bridge, while that of Yihe River and Benghe River laid 53-55 m below near Jiuqu Yihe River Bridge. During the Last Glacial Maximum, Benghe River flowed into Yihe River in the downstream of Jiuqu Yihe River Bridge. The Yihe River’s paleo-valley had a relatively large width-depth ratio which meant a wide and shallow river channel, and it had the characteristics of braided river.